Electronic device having wiring substrate and lead frame

ABSTRACT

An electronic device includes: a first substrate and a second substrate; a lead frame disposed between the first and the second substrates for electrically connecting therebetween; and a first groove and a second groove disposed on the first and the second substrates, respectively. The first and the second grooves correspond to a connection portion between the first and the second substrates and the lead frame. The lead frame is connected to the first and the second substrates in such a manner that one end of the lead frame is engaged in both of the first and the second grooves through a conductive bonding material.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on Japanese Patent Applications No. 2004-6684filed on Jan. 14, 2004, and No. 2004-301406 filed on Oct. 15, 2004, thedisclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an electronic device having a wiringsubstrate and a lead frame.

BACKGROUND OF THE INVENTION

Wire bonding is known as a conventional technique for connecting awiring substrate and lead terminals electrically with each other.According to this conventional technique, a wiring substrate and leadterminals are connected together through wires, but there arises theproblem that an increase of size results because it is necessary toprovide a wire stretching area.

For solving this problem there has been proposed a method wherein awiring substrate and lead terminals are connected together directlythrough a conductive bonding material. However, in the course ofmounting parts onto the wiring substrate or in a resin molding process,a stress may be imposed on the bonded portion, causing a crack or thelike in the bonding portion.

As a countermeasure there has heretofore been proposed a method whereina wiring substrate and lead terminals are connected together directlythrough a conductive bonding material and thereafter a reinforcing resinis applied to the connected, or bonded, portions. This method isdisclosed in, for example, Japanese Patent Application Publication No.2001-210736.

There also has been proposed a method wherein a wiring substrate andlead terminals are connected together directly through a conductivebonding material and thereafter the fixed portions of the lead terminalsare reinforced using an insulating tape. This method is disclosed in,for example, Japanese Patent Application Publication No. 2001-68582.

However, as mentioned above, according to the method wherein a wiringsubstrate and lead terminals are directly connected together through aconductive bonding material and thereafter the connected portions arereinforced using resin or an insulating tape, it is necessary to providea process for disposing the resin or the insulating tape, thus resultingin an increase in the number of processes in the connection between thewiring substrate and the lead terminals.

SUMMARY OF THE INVENTION

In view of the above-described problem, it is an object of the presentinvention to provide an electronic device including a wiring substrateand a lead terminal bonded together through a conductive connectingmaterial. The wiring substrate and the lead terminal are bonded withhigh strength without increasing the number of manufacturing processes.Further, the device has a three-dimensional layout so that thedimensions of the device are reduced.

An electronic device includes: a first substrate and a second substrate,which are laminated each other; a lead frame disposed between the firstand the second substrates for electrically connecting therebetween; anda first groove and a second groove disposed on the first and the secondsubstrates, respectively. The first and the second grooves correspond toa connection portion between the first and the second substrates and thelead frame. The lead frame is connected to the first and the secondsubstrates in such a manner that one end of the lead frame is engaged inboth of the first and the second grooves through a conductive bondingmaterial.

In the above device, the lead frame is connected and engaged in bothgrooves of the first and the second substrates. Therefore, the leadframe is bonded to the first and the second substrates strongly,compared with a conventional device. Further, the groves are formedtogether with manufacturing the first and the second substrates.Therefore, the number of the manufacturing process of the device is notincreased.

Further, the first and the second substrates are laminated each other,and the lead frame is electrically connected to the first and the secondsubstrates. Therefore, multiple electronic parts can be mounted on bothof the first and the second substrates so that the device has athree-dimensional layout. Thus, the dimensions of the device arereduced.

Preferably, the first and the second substrates are laminated substrateshaving a plurality of layers. One of the layers in the first substrateis shorter than the other layers so that the first grooves is provided,the one being disposed utmost outside of the first substrate. One of thelayers in the second substrate is shorter than the other layers so thatthe second grooves is provided, the one being disposed utmost outside ofthe second substrate.

Preferably, the first and the second substrates are laminated substrateshaving a plurality of layers. One of the layers in the first substratehas a concavity so that the first grooves is provided, the one beingdisposed utmost outside of the first substrate, and one of the layers inthe second substrate has a concavity so that the second grooves isprovided, the one being disposed utmost outside of the second substrate.

Preferably, at least one of the first and the second substrates includesa terminal, and the one end of the lead frame includes an extensionportion extending to the terminal of the first or the second substrateso that the extension portion electrically connects to the terminal. Inthis case, the connection resistance as a wiring resistance between thesubstrate and the lead frame can be reduced so that the electricconnection performance therebetween is improved. Further, the frame canbe grounded so that the noise generated in the device is reduced.Furthermore, the frame can provide a large current wiring so that avoltage drop in a wiring of the device and heat generated in the deviceare reduced.

Preferably, the device further includes: a heat radiation plate disposedbetween the first and the second substrates for radiating heat generatedin the first and the second substrates. In this case, the heat radiationplate can improve the heat radiation performance of the first and thesecond substrates.

Further, an electronic device includes: a wiring substrate; a firstelectric part disposed on the wiring substrate; a lead frame connectedto the wiring substrate through a conductive bonding material; and asecond electric part. The wiring substrate includes a groovecorresponding to a connection portion between the wiring substrate andthe lead frame. The lead frame is connected to the substrate in such amanner that one end of the lead frame is engaged in the groove throughthe conductive bonding material. The lead frame has a surface, which isopposite to the connection portion. The second electric part is disposedon the surface of the lead frame. The second electric part electricallyconnects to the wiring substrate.

In the above device, the lead frame is connected and engaged in thegroove of the wiring substrates. Therefore, the lead frame is bonded tothe wiring substrate strongly, compared with a conventional device.Further, the grove is formed together with manufacturing the wiringsubstrates. Therefore, the number of the manufacturing process of thedevice is not increased. Further, multiple electronic parts such as thefirst and the second electric parts can be mounted on the wiringsubstrate and the lead frame so that the device has a three-dimensionallayout. Thus, the dimensions of the device are reduced.

Preferably, the device further includes: a heat radiation plate disposedon the wiring substrate for radiating heat generated in the wiringsubstrate. The heat radiation plate is disposed on a connection portionside of the substrate.

Preferably, the device further includes: a heat sink disposed on aconnection portion side of the substrate; and a resin mold. The leadframe and the heat sink are thermally connected. The resin mold sealsthe first and the second electric parts, the wiring substrate, the leadframe and the heat sink in such a manner that a part of the heat sinkand a part of the lead frame are exposed from the resin mold. Morepreferably, the lead frame and the heat sink are integrated each other.

Further, an electronic device includes: a first wiring substrate; afirst electric part disposed on the first wiring substrate; a casingincluding an inner surface facing the first wiring substrate; a secondwiring substrate disposed on the inner surface of the casing; a secondelectric part disposed on the second wiring substrate; a lead frameconnected to the first wiring substrate through a conductive bondingmaterial; and a groove disposed on the first wiring substrate. Thegroove corresponds to a connection portion between the first wiringsubstrate and the lead frame. The lead frame is connected to the wiringsubstrate in such a manner that one end of the lead frame is engaged inthe groove through the conductive bonding material. The lead frame issupported with the casing. The first wiring substrate is electricallyconnected to the second wiring substrate through the lead frame.

In the above device, the lead frame is bonded to the first wiringsubstrate strongly, compared with a conventional device. Further, thenumber of the manufacturing process of the device is not increased.Furthermore, the device has a three-dimensional layout so that thedimensions of the device are reduced.

Preferably, the device further includes: a heat sink disposed on thecasing. The heat sink provides the inner surface.

Preferably, the casing is made of resin, and the lead frame is supportedwith the casing in such a manner that the lead frame is integrated withthe casing by an insert molding method.

Further, an electronic device includes: a first substrate and a secondsubstrate, which are laminated each other; and a lead frame disposedbetween the first and the second substrates for electrically connectingtherebetween. The lead frame is connected to the first and the secondsubstrates in such a manner that one end of the lead frame is engaged ina connection portion between the first and the second substrates througha conductive bonding material.

In the above device, the lead frame is bonded to the first and thesecond substrates strongly, compared with a conventional device.Further, the number of the manufacturing process of the device is notincreased. Furthermore, the device has a three-dimensional layout sothat the dimensions of the device are reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

FIG. 1 is a cross sectional view showing an electronic device accordingto a first embodiment of the present invention;

FIGS. 2A to 2E are cross sectional views explaining a method formanufacturing the device according to the first embodiment;

FIG. 3 is a cross sectional view showing an electronic device accordingto a second embodiment of the present invention;

FIG. 4 is a plan view on arrow IV in FIG. 3;

FIG. 5 is a plan view on arrow V in FIG. 3;

FIG. 6 is a block diagram showing a circuit system of the electronicdevice according to the second embodiment;

FIG. 7 is a cross sectional view showing an electronic device accordingto a third embodiment of the present invention;

FIG. 8 is a plan view on arrow VIII in FIG. 7;

FIGS. 9A to 9D are cross sectional views explaining a method formanufacturing the device according to the third embodiment;

FIGS. 10A and 10B are cross sectional views explaining the method formanufacturing the device according to the third embodiment;

FIG. 11 is a partial cross sectional view showing an electronic deviceaccording to a fourth embodiment of the present invention;

FIG. 12 is a cross sectional view showing an electronic device accordingto a fifth embodiment of the present invention;

FIG. 13 is a cross sectional view showing an electronic device accordingto a sixth embodiment of the present invention;

FIG. 14 is a cross sectional view showing an electronic device accordingto a seventh embodiment of the present invention;

FIGS. 15A and 15B are plan views showing the device according to theseventh embodiment;

FIG. 16 is a cross sectional view showing an electronic device accordingto an eighth embodiment of the present invention;

FIG. 17 is a plan view showing an electronic device according to a ninthembodiment of the present invention; and

FIG. 18 is a cross sectional view showing an electronic device accordingto a tenth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

FIG. 1 is a diagram showing a schematic sectional construction of anelectronic device S1 according to a first embodiment of the presentinvention.

[Construction, Etc.]

The electronic device S1 shown in FIG. 1 is provided with a pair ofstacked wiring substrates 10 and 20. In the same figure, the upperwiring substrate 10 and the lower wiring substrate 20 are heredesignated a first wiring substrate 10 and a second wiring substrate 20,respectively.

The wiring substrates 10 and 20 are, for example, ceramic substrates orprinted substrates and may be single-layer substrates or laminatedsubstrates (multi-layer substrates). In this embodiment, ceramiclaminate substrates, which are generally known, are adopted as the firstand second wiring substrates 10, 20.

The first and second wiring substrates 10, 20 as ceramic laminatesubstrates are constructed by plural ceramic (e.g., alumina) layers 11,12, 13, 14 and plural like layers 21, 22, 23, 24, respectively.

Although in FIG. 1 the first and second wiring substrates 10, 20comprise four ceramic layers 11 to 14 and 21 to 24, respectively, thenumber of layers is not limited to four insofar as the number of layersis two or more. Of course, five or more layers will do.

The first and second wiring substrates 10, 20 are stacked so thatrespective back surfaces confront each other. In FIG. 1, with respect tothe first wiring substrate 10, the upper surface is a foreside surfaceand the lower surface is a backside surface, while with respect to thesecond wiring substrate 20, the lower surface is a foreside surface andthe upper surface is a backside surface.

Surface wirings 15 and 25 are formed respectively on the surface of thefirst wiring substrate 10 and that of the second wiring substrate 20.Further, in FIG. 1, inner-layer wirings 15 b, 25 b and back wirings 15c, 25 c are formed respectively in the interior and the back surface ofeach of the first and second wiring substrates 10, 20.

These wirings 15 b, 15 c, 25 b, 25 c are conductor patterns formed byprinting, for example, conductor paste and provided on the surfaces,back surfaces, and between adjacent ones of the ceramic layers 11 to 14and of the ceramic layers 21 to 24, in the wiring substrates 10 and 20.In the wiring substrates 10 and 20, the wirings 15 b, 15 c, 25 b, 25 care mutually connected electrically through via holes 15 d, 25 d or thelike formed in the ceramic layers 11 to 14 and 21 to 24.

As shown in FIG. 1, various electronic elements 30, 31 are mounted onthe surfaces of the first and second wiring substrates 10, 20. In thisembodiment, active elements 30 such as semiconductor devices and passiveelements 31 such as resistors and capacitors are mounted on the surfacesof the wiring substrates 10 and 20.

The active elements 30 and the passive elements 31 are fixed onto thesurface wirings 15 and 25 on the surfaces of the wiring substrates 10and 20 through a bonding material 32 such as silver paste or solder. Theactive elements 30 are electrically connected to the surface wirings 15and 25 through bonding wires 33.

Mounting parts such as thick film resistors are mounted on the backsurfaces of the wiring substrates 10 and 20.

Circuits in the wiring substrates 10 and 20 are constructed by all ofthe elements 30 and 31 mounted on the surfaces of the wiring substrates10 and 20, the mounting parts on the back surfaces of the elements 30and 31, the surface wirings 15 and 25, the inner-layer wirings 15 b, 25b, and the back wirings 15 c, 25 c.

Lead frames 40 as lead terminals are interposed between the first andsecond wiring substrates 10, 20 to provide an electric connectionbetween both wiring substrates. The lead frames 40 are composed ofmultiple frames disposed in the vertical direction of the paper surfacein FIG. 1.

As shown in FIG. 1, grooves 16 and 26 are formed in side end portions ofthe back surface of the first wiring substrate 10 and of the backsurface of the second wiring substrate 20 at positions corresponding tothe positions for connection with the lead frames 40.

Connecting end portions of the lead frames 40 for connection with thefirst and second wiring substrates 10, 20 are fitted in the grooves 16and 26 through a conductive bonding material 50, whereby the lead frames40 are bonded to the first and second wiring substrates 10, 20.

That is, the connecting end portions of the lead frames 40 are pinchedby the first and second wiring substrates 10, 20, the grooves 16 and 26are formed in the pinched positions, and the lead frames 40 are fittedin the grooves 16 and 26.

The grooves 16 and 26 are formed by partially removing the ceramiclayers positioned on the back surfaces of the first and second wiringsubstrates 10, 20 out of the plural stacked ceramic layers 11 to 14 and21 to 24 of both wiring substrates.

In the example shown in FIG. 1, the ceramic layers 14 and 24 positionedclosest to the back surfaces of the wiring substrates 10 and 20 arepartially removed from their side end portions to form cutout portionsserving as the grooves 16 and 26.

In case of adopting such a construction using the grooves 16 and 26, forexample the wirings formed in the ceramic layers 13 and 23 as the secondlayers from the back surfaces of the wiring substrates 10 and 20 areexposed into the grooves 16 and 26, serving as connecting electrodes forconnection with the lead frames 40. The wirings as the connectingelectrodes and the lead frames 40 are connected together electricallyand mechanically through the conductive bonding material 50.

The conductive bonding material 50 is not specially limited insofar asit can properly connect the lead frames 40 with the wiring substrates 10and 20 electrically and mechanically. For example, there may be usedsolder, silver paste, a conductive adhesive comprising resin and aconductive filler such as metal contained in the resin, or a brazingfiller metal.

In the electronic device S1, as shown in FIG. 1, the first and secondwiring substrates 10, 20, the elements 30, 31 and other mounting partson the wiring substrates 10 and 20, and the connections between thewiring substrates 10, 20 and the lead frames 40, are enclosed and sealedwith a molding resin 60.

[Manufacturing Method, Etc.]

A method for manufacturing the electronic device S1 of this embodimentwill be described below with reference to FIGS. 2A to 2E. FIGS. 2A to 2Eare process charts showing the manufacturing method, of which FIGS. 2Ato 2D are schematic sectional views and FIG. 2E is an enlargedperspective view of connections between the wiring substrates 10, 20 andthe lead frames 40.

The manufacturing method roughly comprises a process of forming grooves16 and 26 in side end portions of the first and second wiring substrates10, 20 at positions corresponding to the connections between the wiringsubstrates and the lead frames 40, a process of fitting the connectingend portions of the lead frames 40 for connection with the wiringsubstrates 10 and 20 into the first and second grooves 16, 26 throughthe conductive bonding material 50 to connect the lead frames 40 to thewiring substrates 10 and 20, and a resin sealing process.

First, as shown in FIG. 2A, the foregoing via holes and conductorpatterns serving as surface wirings 15, 25, inner-layer wirings 15 b, 25b and back wirings 15 c, 25 c are formed in green sheets serving asceramic layers 11 to 14 and 21 to 24. How to form them may be aconventional method for forming a laminate substrate.

Then, for forming cutout portions serving as grooves 16 and 26, theceramic layers 14 and 24 formed on the back surfaces of the wiringsubstrates 10 and 20 are partially removed. In FIG. 2A, side endportions of one layers positioned closest to the back surfaces arepartially cut off by means of a laser or a punch correspondingly to theexample shown in FIG. 1.

Next, the green sheets are stacked and the resulting laminate is baked,whereby first and second wiring substrates 10, 20 having grooves 16 and26 formed in side edge portions of the back surfaces are fabricated.

In the wiring substrates 10 and 20, where required, a plating treatmentis applied to the surface and back wirings in order to ensure a highmountability of IC, etc., or thick film resistors for example are formedon the back surfaces by printing and baking. Further, if necessary,protection glass is formed, or laser trimming is performed for adjustinga resistance value.

In the example shown in FIG. 2A, wirings 13 a and 23 a which are formedon the ceramic layers 13 and 23 as the second layers from the back sidesof the wiring substrates 10 and 20 are exposed into the grooves 16 and26 as connecting electrodes for connection with the lead frames 40.

The cutting for the green sheets may be done up to a desired layeraccording to a required depth of the grooves 16 and 26. For example, itmay be done for only the first layers from the back surfaces or up tothe third layers.

Then, as shown in FIG. 2B, electronic elements 30 and 31 are mounted onthe surfaces of the wiring substrates 10 and 20. Although only the firstwiring substrate 10 is represented in FIG. 2B, the state of mounting ofthe electronic elements 30 and 31 is the same as in the second wiringsubstrate 20.

In this process of mounting the electronic elements 30 and 31, theactive elements 30 and passive elements 31 are mounted and fixed ontothe surfaces of the wiring substrates 10 and 20 through a bondingmaterial 32 such as silver paste or solder, and bonding wires 33 areformed on the active elements 33 by wire bonding to connect the activeelements 30 and the wiring substrates 10, 20 electrically with eachother.

Next, a process of connecting the lead frames 40 to the first and secondwiring substrates 10, 20 is carried out.

First, as shown in FIGS. 2C and 2E, a conductive bonding material 50 isdisposed within the grooves 16 and 26 of the wiring substrates 10 and20. Although the second wiring substrate 20 is represented in FIG. 2C,the state of disposition of the conductive bonding material 50 is thesame as in the first wiring substrate 10.

The conductive bonding material 50 may be disposed on the lead frame 40side. How to dispose the conductive bonding material 50 is not speciallylimited. For example, printing or dispensing may be adopted.

In case of disposing the conductive bonding material 50 by printing, itis preferable that the conducting material 50 be disposed on the leadframe 40 side. The reason is that, when printing is performed onto thewiring substrates 10 and 20 having such depressions as the grooves 16and 26, there sometimes is a case where the conductive bonding material50 does not smoothly get into the grooves 16 and 26.

Then, as shown in FIG. 2D, connecting end portions of the lead frames 40for connection with the first and second wiring substrates 10 and 20 arefitted into the grooves 16 and 26 through the conductive bondingmaterial 50 while being pinched by both wiring substrates 10, 20.

After the connecting end portions of the lead frames 40 for connectionwith the first and second wiring substrates 10, 20 are thus fitted intothe grooves 16 and 26 through the conductive bonding material 50, theconductive bonding material 50 is cured, whereby the wiring substrates10, 20 and the lead frames 40 are connected together electrically andmechanically.

Thereafter, a resin sealing process is carried out by a transfer moldingmethod using a molding die. In the resin sealing process, the first andsecond wiring substrates 10, 20, the elements and mounting parts on thewiring substrates, and the connections between the wiring substrates 10,20 and the lead frames 40, are sealed with a molding resin 60.

In this state, the individual lead frames 40 are integrally connected toframe portions through tiebars or the like. Therefore, the lead frames40 are separated after the resin sealing with the molding resin 60. Inthis way the electronic device S1 is fabricated.

[Effect, Etc.]

In this embodiment there is provided the electronic device S1 includingthe first and second wiring substrates 10, 20 stacked one on the otherand the lead frames 40 interposed between the first and second wiringsubstrates 10, 20 to provide an electric connection between both wiringsubstrates, wherein grooves 16 and 26 are formed in side end portions ofthe first and second wiring substrates 10, 20 at positions correspondingto connecting portions of the lead frames 40, and connecting endportions of the lead frames 40 for connection with the first and secondwiring substrates 10, 20 are fitted into the grooves 16 and 26 throughthe conductive bonding material 50, whereby the wiring substrates 10, 20and the lead frames 40 are connected together.

Since the lead frames 40 are connected to the first and second wiringsubstrates 10, 20 by being fitted in the grooves 16 and 26, theconnection between the wiring substrates 10, 20 and the lead frames 40can be made stronger than in the prior art.

Particularly, in this embodiment, since the connecting end portions ofthe lead frames 40 are pinched by the first and second wiring substrates10, 20, the connection between the first and second wiring substrates10, 20 and the lead frames 40 can be made stronger, in addition to theeffect of the grooves 16 and 26.

Since the grooves 16 and 26 can be formed simultaneously withfabrication of the first and second wiring substrates 10, 20, as shownin the above manufacturing method, an increase in the number ofprocesses does not occur in connecting the lead frames 40 to the firstand second wiring substrates 10, 20.

Since the first and second wiring substrates 10, 20 are stacked one onthe other and are electrically connected together through the leadframes 40, the electronic elements 30 and 31 can be arranged properly ina three-dimensional form on each of the first and second wiringsubstrates 10, 20.

Thus, according to this embodiment, in connecting the lead frames 40 andthe wiring substrates 10, 20 with each other, not only the connectioncan be made strong without causing an increase in the number ofprocesses, but also the electronic elements 30 and 31 can be arrangedeasily in a three-dimensional form, whereby it is possible to attain thereduction in size of the electronic device.

Moreover, since in this embodiment the lead frames 40 are directlyconnected to the wiring substrates 10 and 20, heat generated for examplefrom the elements 30 and 31 mounted on the wiring substrates 10 and 20can be radiated to the exterior through the lead frames 40.

In the example shown in FIG. 1, the first and second wiring substrates10, 20 are laminate substrates of plural stacked layers 11 to 14 and 21to 24, and the grooves 16 and 26 are formed by partial removal of thelayers 14 and 24 positioned on the outer surface side out of the pluralstacked layers 11 to 14 and 21 to 24.

However, as mentioned earlier, the wiring substrates 10 and 20 used inthis embodiment may be single-layer substrates. Also in this case,grooves can be formed by partially cutting or pressing side end portionsof the substrates.

Second Embodiment

FIG. 3 is a diagram showing a schematic sectional construction of anelectronic device S2 according to a second embodiment of the presentinvention, FIG. 4 is a schematic plan view of the electronic device S2as seen in the direction of arrow IV located at a lower position in FIG.3, and FIG. 5 is a schematic plan view of the electronic device S2 asseen in the direction of arrow V located at an upper position in FIG. 3.In FIGS. 4 and 5, the profile of the molding resin 60 is indicated witha broken line.

[Construction, Etc.]

In the electronic device S2 of this embodiment, the wiring substrate 10is, for example, a ceramic substrate or a printed substrate. It may be asingle-layer substrate or a laminated substrate (multi-layer substrate).In this embodiment, a ceramic laminate substrate, which is generallyknown, is adopted as the wiring substrate 10.

The wiring substrate 10 as a ceramic laminate substrate is constructedby plural ceramic (e.g., alumina) layers 11, 12, 13, and 14. In FIG. 3,an upper surface of the wiring substrate is a surface and a lowersurface thereof is a back surface.

In the example shown in FIG. 3, the wiring substrate 10 comprises fourceramic layers 11 to 14, but the number of constituent layers is notspecially limited insofar as it is two or more. Of course, five or morelayers will do.

Surface wiring 15 is formed on the surface of the wiring substrate 10,while on the back surface of the wiring substrate 10 are formed backelectrodes 15 a as part of back wiring.

The inner-layer wiring 15 b and back wiring 15 c other than the backelectrodes 15 a are formed respectively in the interior and on the backsurface of the wiring substrate 10.

As shown in FIGS. 3 and 5, first electronic elements 30 and 31 aremounted on the surface of the wiring substrate 10. In this embodiment,active elements 30 such as semiconductor devices and passive elements 31such as resistors and capacitors are mounted on the surface of thewiring substrate 10.

The active elements 30 and the passive elements 31 are fixed onto thesurface wiring 15 on the surface of the wiring substrate 10 through abonding material 32 such as silver paste or solder. The active elements30 are electrically connected to the surface wiring 15 through bondingwires 33.

Mounting parts, e.g., thick film resistors, are mounted on the backsurface of the wiring substrate 10. A circuitry in the wiring substrate10 is constructed by all of the first electronic elements 30 and 31mounted on the surface of the wiring substrate 10, the mounting parts onthe back surface of the same wiring substrate, and such wirings as thesurface wiring 15, inner-layer wiring 15 b and back wiring 15 c.

In the wiring substrate 10 with the first electronic elements 30 and 31thus mounted thereon, lead frames 40 as lead terminals are connectedthrough a conductive bonding material 50 to side end portions of theback surface side of the substrate. The lead frames 40 are disposed in aplural number in the vertical direction of the paper surface.

As shown in FIG. 3, grooves 16 are formed in side end portions of theback surface of the wiring substrate 10 at positions corresponding tothe positions for connection with the lead frames 40. Connecting endportions of the lead frames 40 for connection with the wiring substrate10 are fitted in the grooves 16 through the conductive bonding material50, whereby the lead frames 40 are bonded to the wiring substrate 10.

The grooves 16 are formed by partially removing the ceramic layerpositioned on the back surface of the wiring substrate 10 out of theplural stacked ceramic layers 11 to 14.

In the example shown in FIG. 3, the ceramic layer 14 positioned closestto the back surface of the wiring substrate 10 is partially removed fromits side end portions to form cutout portions serving as the grooves 16.

In case of adopting such a construction using the grooves 16, forexample the wiring formed in the ceramic layer 13 as the second layerfrom the back surface of the wiring substrate 10 is exposed into thegroove 16, serving as connecting electrodes for connection with the leadframes 40. The wiring as the connecting electrodes and the lead frames40 are connected together electrically and mechanically through theconductive bonding material 50.

The conductive bonding material 50 is not specially limited insofar asit can properly connect the lead frames 40 with the wiring substrate 10electrically and mechanically. For example there may be used solder,silver paste, a conductive adhesive comprising resin and a conductivefiller such as metal contained in the resin, or a brazing filler metal.

Second electronic elements 34 are connected to the lead frames 40 on theside opposite to the side where the lead frames are connected to thewiring substrate 10. As the second electronic elements 34 there may beadopted, for example, power devices through which a large current, suchas MOSFET or IGBT (insulated gate bipolar transistor).

The second electronic elements 34 and the wiring substrate 10 areelectrically connected with each other. In this embodiment, as shown inFIGS. 3 and 4, the second electronic elements 34 and the back electrodes15 a of the wiring substrate 10 are electrically connected with eachother through bonding wires 35.

Likewise, as shown in FIG. 4, the lead frames 40 with the secondelectronic elements 34 mounted thereon and the lead frames 40 located inthe vicinity thereof are electrically connected with each other throughbonding wires 35.

The bonding wires 35 for connection between the lead frames 34 arethicker than the bonding wires 35 for connection between the secondelectronic elements 34 and the wiring substrate 10 and the bonding wires33 used in the wiring substrate 10.

In the electronic device S2 of this embodiment, as shown in FIGS. 3 to5, the wiring substrate 10, the connections between the wiring substrate10 and the lead frames 40, the first electronic elements 30 and 31 onthe wiring substrate 10, the second electronic elements 34 on the leadframes 40, and the bonding wires 35, are enclosed and sealed with amolding resin 60.

The electronic device S2 is mounted, for example, on an automobile andis applicable as an automobile motor controller. In this case, there maybe adopted such a construction as shown in FIG. 6 in which a controlsection K1 is disposed on the wiring substrate 10 side and a powersection K2 is disposed on the lead frame 40 side.

FIG. 6 is a block diagram showing an example of a circuit system in theelectronic device S2 of this embodiment. The control section K1 isconstructed by a microcomputer and drive element comprising the firstelectronic elements 30 and 31 which are mounted on the wiring substrate10.

On the other hand, the power section K2 is an output circuit constructedby the second electronic elements 34 comprising power transistors whichare mounted on the lead frames 40, and is connected to the foregoingmotor through terminals M+ and M−.

For example, the control section K1 receives a signal from an ECUmounted on an automobile and controls the power section K2 through themicrocomputer and drive element, whereby the motor of the automobile iscontrolled.

[Manufacturing Method, Etc.]

The following description is now provided about a method formanufacturing the electronic device S2 according to this embodiment.

The manufacturing method roughly comprises a process of forming grooves16 in side end portions of the wiring substrate 10 at positionscorresponding to the connections between the wiring substrate and thelead frames 40, a process of fitting the connecting end portions of thelead frames 40 for connection with the wiring substrate 10 into thegrooves 16 through the conductive bonding material 50 to connect thelead frames 40 to the wiring substrate 10, and a resin sealing process.

First, the foregoing via holes 15 d and conductor patterns serving assurface wiring 15, inner-layer wiring 15 b and back wiring 15 cincluding back electrodes 15 a are formed in green sheets serving asceramic layers 11 to 14. How to form them may be a conventional methodfor forming a laminate substrate.

Then, for forming cutout portions serving as grooves 16, the ceramiclayer 14 formed on the back surface of the wiring substrate 10 ispartially removed. In the example shown in FIG. 3, side end portions ofone layer 14 positioned closest to the back surface are partially cutoff by means of a laser or a punch.

Next, the green sheets are stacked and the resulting laminate is baked,whereby the wiring substrate 10 having grooves formed in side endportions of the back surface is fabricated.

In the wiring substrate 10, where required, a plating treatment may beapplied to the surface and back wirings in order to ensure a highmountability of IC, etc., or thick film resistors for example are formedon the back surface by printing and baking. Further, if necessary,protection glass is formed, or laser trimming is performed for adjustinga resistance value.

The cutting for the green sheets may be done up to a desired layeraccording to a required depth of the grooves 16. For example, it may bedone for only the first layer from the back surface or up to the thirdlayer.

Then, first electronic elements 30 and 31 are mounted on the surface ofthe wiring substrate 10. In this process of mounting the firstelectronic elements 30 and 31, the electronic elements 30 and 31 as theactive and passive elements respectively are mounted and fixed onto thesurface of the wiring substrate 10 through a bonding material 32 such assilver paste or solder, and bonding wires 33 are formed on the activeelements 30 by wire bonding to connect the active elements 30 and thewiring substrate 10 electrically with each other.

Next, a process of connecting the lead frames 40 to the wiring substrate10 and mounting the second electronic elements 34 onto the lead frames40 is carried out. The mounting and fixing of the second electronicelements 34 to the lead frames 40 can be done using a bonding materialsuch as silver paste or solder and it is optional whether the saidmounting and fixing are to be performed before or after the bondingbetween the wiring substrate 10 and the lead frames 40.

In connecting the wiring substrate 10 and the lead frames 40 with eachother, first a conductive bonding material 50 is disposed within thegrooves 16 of the wiring substrate 10. The conductive bonding material50 may be disposed on the lead frame 40 side. How to dispose theconductive bonding material 50 is not specially limited. For example,printing or dispensing may be adopted.

In case of disposing the conductive material 50 by printing, it ispreferable that the conductive bonding material 50 be disposed on thelead frame 40 side. The reason is that, when printing is performed ontothe wiring substrate 10 having such depressions as the grooves 16, theresometimes is a case where the conductive bonding material 50 does notsmoothly get into the grooves 16.

Then, connecting end portions of the lead frames 40 for connection withthe wiring substrate 10 are fitted into the grooves 16 through theconductive bonding material 50. Thereafter, the conductive bondingmaterial 50 is cured, whereby the wiring substrate 10 and the leadframes 40 are connected together electrically and mechanically.

Subsequently, a resin sealing process is carried out by a transfermolding method using a molding die. In the resin sealing process, thewiring substrate 10, the connections between the wiring substrate 10 andthe lead frames 40, the first electronic elements 30 and 31 on thewiring substrate 10, the second electronic elements 34 on the leadframes 40, and the bonding wires 35, are sealed with a molding resin 60.

In this state, the individual lead frames 40 are integrally connected toframe portions through tiebars or the like. Therefore, the lead frames40 are separated after the resin sealing with the molding resin 60. Inthis way the electronic device S2 is fabricated.

[Effect, Etc.]

In this embodiment there is provided the electronic device S2 includingthe wiring substrate 10 with the first electronic elements 30 and 31mounted thereon and the lead frames 40 bonded to the wiring substrate 10through the conductive bonding material 50, wherein grooves 16 areformed in side end portions of the wiring substrate 10 at positionscorresponding to connecting portions of the lead frames 40, andconnecting end portions of the lead frames 40 for connection with thewiring substrate 10 are fitted into the grooves 16 through theconductive bonding material 50, whereby the wiring substrate 10 and thelead frames 40 are connected together, further, the second electronicelements 34 are mounted on the lead frames 40 on the side opposite tothe side where the lead frames are connected to the wiring substrate 10,the second electronic elements 34 being electrically connected to thewiring substrate 10.

Since the lead frames 40 are connected to the wiring substrate 10 bybeing fitted in the grooves 16, the connection between the wiringsubstrate 10 and the lead frames 40 can be made stronger than in theprior art.

Since the grooves 16 can be formed simultaneously with fabrication ofthe wiring substrate 10, an increase in the number of processes does notoccur in connecting the lead frames 40 to the wiring substrate 10.

Since the first electronic elements 30 and 31 are mounted on the surfaceof the wiring substrate 10 and the second electronic elements 34 aremounted on the lead frames 40 on the side opposite to the wiringsubstrate 10, further, the second electronic elements mounted on thelead frames 40 are electrically connected to the wiring substrate 10,the electronic elements 30, 31, and 34 can be arranged in athree-dimensional form.

Thus, according to this embodiment, in connecting the lead frames 40 andthe wiring substrate 10 with each other, not only the strength of theconnection can be made strong without causing an increase in the numberof processes, but also the electronic elements 30, 31 and 34 can bearranged easily in a three-dimensional form, whereby it is possible toattain the reduction in size of the electronic device.

In this embodiment, moreover, since the lead frames 40 are directlyconnected to the wiring substrate 10, heat generated for example fromthe first electronic elements 30 and 31 mounted on the wiring substrate10 can be radiated to the exterior through the lead frames 40.

Although in the example shown in FIGS. 3 to 5 the second electronicelements 34 mounted on the lead frames 40 and the wiring substrate 10are electrically connected with each other through the bonding wires 35,the means for the electric connection is not limited to the bondingwires.

In the example shown in FIG. 3, the wiring substrate 10 is a laminatesubstrate of plural stacked layers 11 to 14 and the grooves 16 areformed by partial removal of the layer 14 positioned on the outersurface side out of the plural stacked layers 11 to 14.

However, as mentioned above, the wiring substrate 10 used in thisembodiment may be a single-layer substrate. Also in this case, groovescan be formed by partially cutting or pressing the side end portions ofthe substrate.

Third Embodiment

FIG. 7 is a diagram showing a schematic sectional construction of anelectronic device S3 according to a third embodiment of the presentinvention and FIG. 8 is a schematic plan view of the electronic deviceS3 as seen in the direction of arrow VIII located at an upper positionin FIG. 7.

[Construction, Etc.]

In the electronic device S3 of this embodiment, a first wiring substrate10 is, for example, a ceramic substrate or a printed substrate and maybe a single-layer substrate or a laminated substrate (multi-layersubstrate). In this embodiment, a ceramic laminate substrate, which isgenerally known, is adopted as the first wiring substrate 10.

The first wiring substrate 10 as the ceramic laminate substrate isconstructed by plural ceramic (e.g., alumina) layers 11, 12, 13, and 14.In FIG. 7, as to the first wiring substrate 10, the lower surface is asurface and the upper surface is a back surface.

In the example shown in FIG. 7, the first wiring substrate 10 comprisesfour ceramic layers 11 to 14, but the number of layers is not limited tofour insofar as the number of layers is two or more. Of course, five ormore layers will do.

Surface wiring 15 is formed on the surface of the first wiring substrate10. Further, in FIGS. 7 and 8, inner-layer wiring 15 b and back wiring15 c are formed respectively in the interior and the back surface of thefirst wiring substrate 10.

As shown in FIG. 7, first electronic elements 30 and 31 are mounted onthe surface of the first wiring substrate 10. In this embodiment, activeelements 30 such as semiconductor devices and passive elements 31 suchas resistors and capacitors are mounted on the surface of the firstwiring substrate 10.

The active elements 30 and the passive elements 31 are fixed onto thesurface wiring 15 on the surface of the first wiring substrate 10through a bonding material 32 such as silver paste or solder. The activeelements 30 are electrically connected to the surface wiring 15 throughbonding wires 33.

Mounting parts such as thick film resistors are mounted on the backsurface of the first wiring substrate 10. A circuitry in the firstwiring substrate 10 is constructed by all of the first electronicelements 30 and 31 mounted on the surface of the first wiring substrate10, the mounting parts mounted on the back surface of the first wiringsubstrate, and such wirings as the surface wiring 15, inner-layer wiring15 b and back wiring 15 c.

Lead frames 40 as lead terminals are connected through a conductivebonding material 50 to side end portions on the surface side of thefirst wiring substrate 10 with the first electronic elements 30 and 31mounted thereon. The lead frames 40 are arranged in a plural number inthe vertical direction of the paper surface in FIG. 7.

As shown in FIG. 7, grooves 16 are formed in side end portions of theback surface of the first wiring substrate 10 at positions correspondingto the positions for connection with the lead frames 40. Connecting endportions of the lead frames 40 for connection with the first wiringsubstrate 10 are fitted in the grooves 16 through the conductive bondingmaterial 50, whereby the lead frames 40 are bonded to the first wiringsubstrate 10.

The grooves 16 are formed by partially removing the ceramic layerpositioned on the surface side of the first wiring substrate 10 out ofthe plural ceramic layers 11 to 14.

In the example shown in FIG. 7, the ceramic layer 11 positioned closestto the surface of the first wiring substrate 10 is partially removedfrom its side end portions to form cutout portions serving as thegrooves 16.

In case of adopting such a construction using the grooves 16, forexample, the wiring formed in the ceramic layer 12 as the second layerfrom the surface side of the wiring substrate 10 are exposed into thegrooves 16, serving as connecting electrodes for connection with thelead frames 40. The wiring as the connecting electrodes and the leadframes 40 are connected together electrically and mechanically throughthe conductive bonding material 50.

The conductive bonding material 50 is not specially limited insofar asit can properly connect the lead frames 40 with the first wiringsubstrate electrically and mechanically. For example, there may be usedsolder, silver paste, a conductive adhesive comprising resin and aconductive filler such as metal contained in the resin, or a brazingfiller metal.

As shown in FIG. 7, the lead frames 40 are supported by the case 70. Thecase 70 is a resin or ceramic case beforehand molded integrally with thelead frames 40. In this embodiment, the case 70 is a resin case and thelead frames 40 are united with the case 70 by insert molding and aresupported thereby.

The case 70 has an opposed surface 70 a opposed to the first wiringsubstrate 10. The case 70 is provided with a heat sink 71, which isfixed, for example by adhesive bonding, to the support portion of thecase for supporting the lead frames 40. One surface of the heat sink 71is constructed as the opposed surface 70 a of the case 71.

A second wiring substrate 20 is provided on the opposed surface 70 a ofthe case 70. The second wiring substrate 20 is fixed by bonding througha heat conductive bonding material 72 to the heat sink 71 as the opposedsurface 70 a.

The second wiring substrate 20 is also a ceramic substrate or a printedsubstrate and may be a single-layer substrate or a laminated substrate(multi-layer substrate). In this embodiment, a single-layer ceramicsubstrate, which is generally known, is adopted as the second wiringsubstrate 20.

Second electronic elements 34 are mounted on the second wiring substrate20. As the second electronic elements 34 there may be adopted, forexample, power devices through which a large current, such as MOSFETs orIGBTs (insulated gate bipolar transistors).

The first wiring substrate 10 and the second wiring substrate 20 areconnected with each other electrically through the lead frames 40. Inthis embodiment, as shown in FIGS. 7 and 8, electrodes 20 a of thesecond wiring substrate 20 and the lead frames 40 are electricallyconnected with each other through bonding wires 35.

In the electronic device S3 of this embodiment, as shown in FIGS. 7 and8, the first wiring substrate 10, the connections between the firstwiring substrate 10 and the lead frames 40, the first electronicelements 30 and 31 on the first wiring substrate 10, the second wiringsubstrate 20, the second electronic elements 34 on the second wiringsubstrate 20, and the bonding wires 35, are enclosed and sealed with amolding resin 60.

The electronic device S3 may also be mounted for example on anautomobile and applied as a controller for an automobile motor. In thiscase, as shown in FIG. 6, the electronic device S3 may be constructed soas to include the control section K1 and the power section K2, theformer being disposed on the first wiring substrate 10 side and thelatter on the second wiring substrate 20 side.

FIG. 6 is also represented as a block diagram showing an example of acircuit system in the electronic device S3 of this embodiment, in whichthe control section K1 is constructed by a microcomputer and driveelement comprising the first electronic elements 30 and 31, which aremounted on the first wiring substrate 10.

On the other hand, the power section K2 is an output circuit constructedby the second electronic elements 34 comprising power transistors whichare mounted on the second wiring substrate 20, and is connected to theforegoing motor through terminals M+ and M−.

For example, the control section K1 receives a signal from an ECUmounted on an automobile and controls the power section K2 through themicrocomputer and drive element, whereby the motor of the automobile iscontrolled.

[Manufacturing Method, Etc.]

A method for manufacturing the electronic device S3 of this embodimentwill be described below with reference to FIGS. 9A to 9D and 10A, 10B.FIGS. 9A to 9D are process diagrams showing the manufacturing method andFIGS. 10A and 10B are process diagrams showing the manufacturing methodand following the process diagrams of FIGS. 9A to 9D.

As shown in FIG. 9A, the foregoing via holes and conductor patternsserving as surface wiring 15, inner-layer wiring 15 b and back wiring 15c are formed in green sheets serving as ceramic layers 11 to 14 in thefirst wiring substrate 10. How to form them may be a conventional methodfor forming a laminate substrate.

Then, for forming cutout portions serving as grooves 16, the ceramiclayer 11 positioned on the surface side of the first wiring substrate 10is partially removed. In FIG. 9A, correspondingly to the example shownin FIG. 7, side end portions of one layer 11 positioned closest to thesurface of the first wiring substrate are partially cut off by means ofa laser or a punch.

Next, the green sheets are stacked and the resulting laminate is baked,whereby grooves 16 are formed in side end portions on the surface sideof the first wiring substrate 10.

In the first wiring substrate 10, where required, a plating treatment isapplied to the surface and back wirings in order to ensure a highmoutability of IC, etc., or thick film resistors for example are formedon the back surface by printing and baking. Further, if necessary,protection glass is formed, or laser trimming is performed for adjustinga resistance value.

The cutting for the green sheets may be done up to a desired layeraccording to a required depth of the grooves 16. For example, it may bedone for only the first layer from the surface side or up to the thirdlayer.

Then, first electronic elements 30 and 31 are mounted on the surface ofthe first wiring substrate 10. In this process of mounting the firstelectronic elements 30 and 31, the first electronic elements 30 and 31as the active and passive elements respectively are mounted and fixedonto the surface of the first wiring substrate 10 through a bondingmaterial 32, and bonding wires 33 are formed on the active elements 30by wire bonding to connect the active elements and the wiring substrate10 electrically with each other. The state so far obtained is shown inFIG. 9A.

On the other hand, as shown in FIG. 9B, second electronic elements 34are mounted on the second wiring substrate 20. Also in this process ofmounting the second electronic elements 34, the second electronicelements 34 are mounted and fixed through a bonding material such assilver paste or solder onto the surface of the second wiring substrate20.

Then, as shown in FIG. 9C, the second wiring substrate 20 with thesecond electronic elements 34 mounted thereon is mounted and fixed bybonding through a heat conducting bonding material 72 onto the surfaceof the heat sink 71 serving as the opposed surface 70 a of the case 70.

On the other hand, as shown in FIG. 9D, lead frames 40 are formed in thecase 70 by insert molding.

Then, as shown in FIG. 10A, the heat sink 70 is fixed to and united withthe case 70 which supports the lead frames 40, through an adhesive orthe like. Subsequently, wire bonding is performed to provide an electricconnection between the electrodes 20 a on the second wiring substrate 20and the lead frames 40 through bonding wires 35.

Next, as shown in FIG. 10B, the first wiring substrate 10 and the leadframes 40 are connected with each other.

First, a conductive bonding material 50 is disposed within the grooves16 of the first wiring substrate 10. The conductive bonding material 50may be disposed on the lead frame 40 side. How to dispose the conductivebonding material 50 is not specially limited. For example, printing ordispensing may be adopted.

In case of disposing the conductive bonding material 50 by printing, itis preferable that the conductive bonding material 50 be disposed on thelead frame 40 side. The reason is that, when printing is performed ontothe wiring substrate 10 having such depressions as the grooves 16, theresometimes is a case where the conductive bonding material 50 does notsmoothly get into the grooves 16.

Then, connecting end portions of the lead frames 40 for connection withthe wiring substrate 10 are fitted into the grooves through theconductive bonding material 50. Thereafter, the conductive bondingmaterial 50 is cured, whereby the first wiring substrate 10 and the leadframes 40 are connected together electrically and mechanically.

Subsequently, a resin sealing process is carried out, whereby the firstwiring substrate 10, the connections between the first wiring substrate10 and the lead frames 40, the first electronic elements 30 and 31 onthe first wiring substrate 10, the second wiring substrate 20, thesecond electronic elements 34 on the second wiring substrate 20, and thebonding wires 35, are sealed with a molding resin 60. In this way theelectronic device S3 is fabricated.

[Effect, Etc.]

According to this embodiment there is provided the electronic device S3,which is characterized by the following points.

The electronic device S3 is provided with the first wiring substrate 10with the first electronic elements 30 and 31 mounted thereon and thelead frames 40 connected to the first wiring substrate 10 through theconductive bonding material 50.

The grooves 16 are formed in the side end portions of the first wiringsubstrate 10 at positions corresponding to the connections between thewiring substrate and the lead frames 40, and the connecting end portionsof the lead frames 40 for connection with the first wiring substrate 10are fitted in the grooves 16 through the conductive bonding material 50,whereby the first wiring substrate 10 and the lead frames 40 areconnected with each other.

The lead frames 40 are supported by the case 70, the case 70 has theopposed surface 70 a opposed to the first wiring substrate 10, and thesecond wiring substrate 20 is provided on the opposed surface 70 a ofthe case 70.

The second electronic elements 34 are mounted on the second wiringsubstrate 20, and the first and second wiring substrates 10, 20 areelectrically connected with each other through the lead frames 40.

According to the electronic device S3 characterized by the above points,since the lead frames 40 are connected to the first wiring substrate 10by being fitted into the grooves 16, the connection between the firstwiring substrate 10 and the lead frames 40 can be made stronger than inthe prior art.

As shown in the above manufacturing method, the grooves 16 can be formedsimultaneously with fabrication of the first wiring substrate 10, sothat an increase in the number of processes does not occur in connectingthe lead frames 40 to the first wiring substrate 10.

Since the first electronic elements 30, 31 and the second electronicelements 34 are mounted respectively on the first wiring substrate 10and the second wiring substrate 20 provided on the opposed surface 70 aof the case 70 which is opposed to the first wiring substrate 10, andsince the second wiring substrate 20 is connected to the first wiringsubstrate 10 electrically through the lead frames 40, the electronicelements 30, 31, and 34 can be arranged in a three-dimensional form.

Thus, according to this embodiment, in connecting the lead frames 40 andthe wiring substrates 10, 20 with each other, not only the connectioncan be made strong without causing an increase in the number ofprocesses, but also the electronic elements 30, 31, and 34 can bearranged easily in a three-dimensional form, whereby it is possible toattain the reduction in size of the electronic device.

In this embodiment, moreover, since the lead frames 40 are directlyconnected to the first wiring substrate 10, heat generated for examplefrom the first electronic elements 30 and 31 mounted on the first wiringsubstrate 10 can be radiated to the exterior through the lead frames 40.

In the above illustrated example, since the case 70 is provided with theheat sink 71 and one surface of the heat sink 71 is constructed as theopposed surface 70 a of the case 70, it is possible to improve the heatdissipating property of the second wiring substrate 20 which is providedon the opposed surface 70 a of the case 70.

Although in the above illustrated example the second wiring substrate 20and the lead frames 40 are electrically connected together through thebonding wires 35, the means for such an electric connection is notlimited to the bonding wires.

In the above illustrated example the first wiring substrate 10 is alaminate substrate of plural stacked layers 11 to 14 and the grooves 16are formed by partially removing the layer 14 positioned on the outersurface side out of the plural stacked layers 11 to 14.

However, as mentioned earlier, the first wiring substrate 10 used inthis embodiment may be a single-layer substrate. Also in this case, thegrooves can be formed by partially cutting or pressing the side endportions of the substrate.

Fourth Embodiment

FIG. 11 is a diagram showing a schematic sectional construction of aprincipal portion of an electronic device according to a fourthembodiment of the present invention.

In the above embodiments the grooves 16 are formed in the side endportions of the wiring substrate 10 (20) at positions corresponding tothe connecting portions for connection with the lead frames 40, and thewiring substrate 10 (20) and the lead frames 40 are connected togetherby fitting the connecting end portions of the lead frames 40 into thegrooves 16 through the conductive bonding material 50.

In this embodiment, as shown in FIG. 11, not only the grooves 16 areformed in the wiring substrate 10, but also grooves 41 are formed in theconnecting end portions of the lead frames 40, and the grooves 16 of thewiring substrate 10 and the grooves 41 of the lead frames 40 are engagedwith each other through the conductive bonding material 50, whereby thesubstrate 10 and the lead frames 40 are connected with each other.

This embodiment is applicable to any wiring substrate insofar as thewiring substrate used is connected to the lead frames 40, such as thewiring substrates 10 and 20 described in the first embodiment, thewiring substrate 10 described in the second embodiment, and the firstwiring substrate 10 described in the third embodiment.

As result, when connecting the lead frames 40 to the wiring substrate10, it is possible to improve the positioning performance and bondingstrength of the two.

Fifth Embodiment

FIG. 12 is a diagram showing a schematic sectional construction of anelectronic device S11 according to a fifth embodiment of the presentinvention. The electronic device S11 of this embodiment corresponds to apartial modification of the electronic device S1 of the firstembodiment. A description will be given below mainly about a differentpoint between the two.

In the electronic device S11, terminals 17 are provided on the backsurface(s) of one or both of the first and second wiring substrates 10,20, i.e., on the surface(s) for connection with the lead frames 40, leadframes 40 are partially extended as extending portions 42 up to theterminals 17, and the extending portions 42 and the terminals 17 areelectrically connected with each other.

In the example shown in FIG. 12, terminals 17 are provided on theconnection surface of the first wiring substrate 10 for connection withthe lead frames 40, and the extending portions 42 of lead frames 40 andthe terminals 17 are electrically connected with each other through aconductive bonding material 51.

The terminals 17 are electrically connected to the surface wirings 15and 25 through the inner-layer wiring 15 b, 25 b and back wiring 15 c,25 c formed on the wiring substrates 10 and 20 to constitute a circuit.It is apparent that the same construction can be adopted also for thesecond wiring substrate 20.

According to this embodiment, the wiring resistance between the wiringsubstrates 10, 20 and the lead frames 40 can be made low and theconnectability between the two can be improved. When the potential ofthe terminals 17 is set at GND potential, the resistance to noiseimproved, and when the terminals 17 are made large current wiring, it ispossible to suppress a lowering of voltage and the generation of heat inthe wiring. Besides, circuit characteristics can be improved.

Sixth Embodiment

FIG. 13 is a diagram showing a schematic sectional construction of anelectronic device S21 according to a sixth embodiment of the presentinvention. The electronic device S21 of this embodiment corresponds to apartial modification of the electronic device S2 of the secondembodiment. A description will be given below mainly about a differentpoint between the two.

The electronic device S21 of this embodiment corresponds to theapplication of the fifth embodiment to the second embodiment. Morespecifically, in the electronic device S21 of this embodiment, terminals17 are provided on the back surface of the wiring substrate 10, i.e., onthe connection surface of the wiring substrate 10 for connection withthe lead frames 40, lead frames 40 are partially extended as extendingportions 42 up to the terminals 17, and the extending portions 42 andthe terminals 17 are electrically connected with each other.

In the example shown in FIG. 13, terminals 17 are provided on theconnection surface of the wiring substrate 10 for connection with thelead frames 40, and the extending portions 42 of lead frames 40 and theterminals 17 are electrically connected with each other through aconductive bonding material 51.

The terminals 17 are electrically connected to the surface wirings 15and 25 through the inner-layer wiring 15 b, 25 b and back wiring 15 c,25 c formed on the wiring substrate 10 to constitute a circuit.

Also according to this embodiment, the wiring resistance between thewiring substrate 10 and the lead frames 40 can be made low and theconnectability between the two can be improved. Besides, the resistanceto noise is improved by setting the potential of the terminals at GNDpotential. Moreover, by making the terminals 17 a large current wiring,it is possible to suppress a lowering of voltage and the generation ofheat in the wiring. Further, circuit characteristics can be improved.

It is apparent that the construction of the lead frames 40 having theextending portions 42 is applicable also to the electronic device S3 ofthe third embodiment shown in FIG. 7.

For example, the same terminals 17 as above may be provided on theconnection surface of the first wiring substrate 10 for connection withthe lead frames 40 at positions avoiding various electronic elements inFIG. 17, the same extending portions 42 as above extending up to theterminals 17 may be formed on lead frames 40, and the extending portions42 and the terminals 17 may be electrically connected with each other.

Seventh Embodiment

FIG. 14 is a diagram showing a schematic sectional construction of anelectronic device S12 according to a seventh embodiment of the presentinvention. The electronic device S12 of this embodiment corresponds to apartial modification of the electronic device S1 of the firstembodiment. A description will be given below mainly about a differentpoint between the two.

In the electronic device S12 of this embodiment, a heat dissipatingplate 43 connected thermally to the first and second wiring substrates10, 20 is interposed between both wiring substrates 10 and 20, and heatgenerated from both wiring substrates 10, 20 can be dissipated throughthe heat dissipating plate 43.

More specifically, in the example shown in FIG. 14, the heat dissipatingplate 43 such as a Cu plate is connected to both wiring substrates 10and 20 through a heat conducting bonding material 53, e.g., solder or aresin adhesive.

The provision of the heat dissipating plate 43 is preferred because theheat dissipating performance of both wiring substrates 10 and 20 can beimproved.

In the example shown in FIG. 14, substantially the whole of the deviceis sealed with a molding resin 60, but it is preferable that a part ofthe heat dissipating plate 43 be exposed from the molding resin 60 orconnected thermally to an external heat dissipating member.

FIGS. 15A and 15B are plan views showing examples of an exposed form ofthe heat dissipating plate 43 from the molding resin 60.

In the example shown in FIG. 15A, the heat dissipating plate 43 has combteeth-like projecting portions 44 projecting from the molding resin 60.The projecting portions 44 may be formed by molding integrally with arectangular body of the heat dissipating plate 44 or may be bonded tothe body by caulking or welding. Heat generated from the heatdissipating plate 43 is allowed to escape from the projecting portions44 to the exterior of the molding resin 60.

The projecting portions 44 are provided on the four sides of therectangular heat dissipating plate 43. On the sides where the leadframes 40 are present, the projecting portions 44 are each providedbetween adjacent lead frames 40.

In the example shown in FIG. 15B, a rectangular heat dissipating plate43 is larger in size so as to project from the molding resin 60 on twosides where the lead frames 40 are not present. Also in this case, heatis allowed to escape from the projecting portions to the exterior of themolding resin 60.

Eighth Embodiment

FIG. 16 is a diagram showing a schematic sectional construction of anelectronic device S22 according to an eighth embodiment of the presentinvention. The electronic device S22 of this embodiment corresponds to apartial modification of the electronic device S1 of the firstembodiment. A description will be given below mainly about a differentpoint between the two.

The electronic device S22 of this embodiment corresponds to theapplication of the seventh embodiment to the second embodiment. Morespecifically, in the electronic device S22 of this embodiment, a heatdissipating plate 43 connected thermally to the wiring substrate 10 isdisposed on the back surface of the wiring substrate 10, i.e., on theconnection surface of the wiring substrate 10 for connection with thelead frames 40, and heat from the wiring substrate 10 can be dissipatedthrough the heat dissipating plate 43.

In the example shown in FIG. 16, the heat dissipating plate 43 such as aCu plate is connected to the wiring substrate 10 through a heatconducting bonding material 53, e.g., solder or a resin adhesive.

This construction is preferred because the heat dissipating performanceof the wiring substrate 10 can be improved by the heat dissipating plate43.

In the example shown in FIG. 16, substantially the whole of the deviceis sealed with a molding resin 60, but it is preferable that a part ofthe heat dissipating plate 43 be exposed from the molding resin 60 orconnected thermally to an external heat dissipating member. This modemay be the same as that of the example shown in FIGS. 15A and 15B.

Ninth Embodiment

FIG. 17 is a diagram showing a schematic sectional construction of aprincipal portion of an electronic device according to a ninthembodiment of the present invention. The construction shown in FIG. 17corresponds to a partial modification of the electronic device S2 of thesecond embodiment shown in FIG. 4, but this embodiment is applicablealso to the electronic device of the first embodiment.

In the first and second embodiments, connecting end portions of the leadframes 40 for connection with the wiring substrates 10 and 20 are fittedinto the grooves 16 and 26 through the conductive bonding material 50,whereby the wiring substrates 10, 20 and the lead frames 40 areconnected together.

As in this embodiment shown in FIG. 17, portions free of the grooves 16may be provided in the wiring substrate 10 and lead frames 40 a may beelectrically connected to the grooves-free portions through a conductivebonding material 50 for example.

According to this construction, the lead frames 40 a can be connected tothe wiring substrates 10 and 20 even at such portions as cannot begrooved.

Tenth Embodiment

FIG. 18 is a diagram showing a schematic sectional construction of anelectronic device S23 according to a tenth embodiment of the presentinvention. The electronic device S23 of this embodiment corresponds to apartial modification of the electronic device S2 of the secondembodiment.

In the electronic device S23 of this embodiment, a heat sink 45 isprovided on the connection surface side of the wiring substrate 10 forconnection with the lead frames 40, and the lead frames 40 are thermallyconnected to the heat sink 45. Further, the first electronic elements30, 31, the wiring substrate 10, the second electronic elements 34, thelead frames 40, and the heat sink 45, are sealed with the molding resin60 so that the heat sink 45 and the lead frames 40 are partiallyexposed.

In the example shown in FIG. 18, the lead frames 40 and the heat sink 45are formed integrally by molding and are thereby connected togetherthermally. Of course, the lead frames 40 and the heat sink 45 may beformed separately and connected together thermally by, for example,caulking or welding.

The heat sink 45 and the wiring substrate 10 are thermally connectedtogether through an adhesive 54 and heat generated from the wiringsubstrate 10 escapes through the heat sink 45. In this embodiment, thesecond electronic elements 34 and the wiring substrate 10 can beconnected together electrically by wire bonding at positions not shown.

According to this embodiment, the heat dissipating performance of thedevice S23 can be ensured properly in case of the device being aresin-sealed type electronic device. This is preferable.

Other Embodiments

Although in the above embodiments the wiring substrates 10 and 20 aremainly constructed by laminate substrates, the wiring substrates 10 and20 may be thick film substrates or printed resin substrates. Further, inthe embodiments using plural wiring substrates, different types ofsubstrates such as laminates substrate, thick film substrate, andprinted resin substrate, may be combined as the wiring substrates.

Such changes and modifications are to be understood as being within thescope of the present invention as defined by the appended claims.

1. An electronic device comprising: a first substrate and a secondsubstrate; a lead frame disposed between the first and the secondsubstrates for electrically connecting therebetween; and a first grooveand a second groove disposed on the first and the second substrates,respectively, wherein the first and the second grooves correspond to aconnection portion between the first and the second substrates and thelead frame, and the lead frame is connected to the first and the secondsubstrates in such a manner that one end of the lead frame is engaged inboth of the first and the second grooves through a conductive bondingmaterial.
 2. The device according to claim 1, wherein the first and thesecond substrates are laminated substrates having a plurality of layers,one of the layers in the first substrate is shorter than the otherlayers so that the first grooves is provided, the one being disposedutmost outside of the first substrate, and one of the layers in thesecond substrate is shorter than the other layers so that the secondgrooves is provided, the one being disposed utmost outside of the secondsubstrate.
 3. The device according to claim 1, wherein the first and thesecond substrates are laminated substrates having a plurality of layers,one of the layers in the first substrate has a concavity so that thefirst grooves is provided, the one being disposed utmost outside of thefirst substrate, and one of the layers in the second substrate has aconcavity so that the second grooves is provided, the one being disposedutmost outside of the second substrate.
 4. The device according to claim1, wherein at least one of the first and the second substrates includesa terminal, and the one end of the lead frame includes an extensionportion extending to the terminal of the first or the second substrateso that the extension portion electrically connects to the terminal. 5.The device according to claim 1, further comprising: a heat radiationplate disposed between the first and the second substrates for radiatingheat generated in the first and the second substrates.